Dauntless is a scientist exposed to a exrtreme variety of Aether a entity of the Aether enters his mind and possesses his body during combat. Mutant Juggernaut/Esper Symboite
(First Image is him at 16. Second Image is him at 40)
Marcus Hashido was part of the original class 1-A with the love of his Life Elizabeth Todoroki. (I'll make lore of her once I have art) Him and Elizabeth's were equals in terms of raw firepower and strength. They were great friends with the Main cast but during the Hospital raid he was Kidnapped by a high grade Nomu and he was turned into the backup incase shigraki Failed. AFO in the final war had to fight Elizabeth to the death and unfortunately won the fight taking Elizabeths power then slicing her in half. This made Marcus destroy kill the version of AFO in his body. He fully embraced being a villain and killed half of Japan's heros a couple years later. In his Early thirties he created seven children with his DNA and Elizabeth's DNA. They became the seven sins of conquest the largest villain family in Japan. While his children run his empire his third oldest son helps him Genetically modify his body for 10 years becoming the perfect being